NSA spying: phone “metadata” yields private details

Pres. Obama has tried to reassure Americans that the telephone records collected en masse by the National Security Agency don’t include the contents of calls — only the dry, impersonal “metadata.”

Photo: AP

But can that data — the numbers you call, the length of conversations, the location of your phone — reveal details of your private life?

Two Stanford graduate students gathered three months of phone metadata from 546 volunteers and started sifting. They were able to spot someone suffering from multiple sclerosis, a caller with a fondness for a particular type of assault rifle and a person who appeared to be running a marijuana grow house.

“What surprised us was how much sensitive information was crammed into the metadata,” said Jonathan Mayer, a PhD candidate and a cybersecurity fellow at the school’s Center for International Security and Cooperation. “We didn’t think there’d be that much.”

Others have reached similar conclusions.

In some ways, teasing personal details out of metadata can be easier than combing through the actual content of calls, texts and e-mails. Content can be written or spoken in multiple languages, and it doesn’t follow any standard structure. Metadata, in contrast, is highly structured and can be quickly sifted.

“Many details of our lives can be gleaned by examining those (metadata) trails, which often yield information more easily than do the actual content of our communications,” wrote Edward Felten, a Princeton University professor, testifying last year in a court case challenging the NSA program.

“Superimposing our metadata trails onto the trails of everyone within our social group and those of everyone within our contacts’ social groups, paints a picture that can be startlingly detailed,” he wrote.

Former NSA contractor Edward Snowden revealed the far-reaching metadata surveillance program last year. Late Monday, the New York Times reported that the Obama administration would propose ending the systematic collection of phone metadata, instead collecting specific records only under a new kind of court order from a judge.

Mayer and his colleague Patrick Mutchler took the volunteers’ phone records and used publicly available data from Google and Yelp to identify numbers that the volunteers called. Patterns quickly emerged.

“We found one person who called a lumber yard, a hydroponics store and a bong shop,” Mayer said. “It doesn’t take much imagination to think what might be going on there.”

Another volunteer called multiple gun shops, including one that specialized in a particular type of assault rifle. The same volunteer also called the customer support line for the company that makes that rifle.

“Certainly if a couple of graduate students can map phone numbers to businesses this easily, an agency with the resources of the NSA can,” Mayer said.